1. Field of the Invention
This invention relates to an apparatus and method for testing for blockages in fluid passages in internal combustion engines in general and, in particular, for testing for blockages in cooling passages in cylinder heads for internal combustion engines.
2. Summary of the Prior Art
Recent trends in automotive design have seen the use of smaller internal combustion engines to reduce the overall size of the engine compartment required to house the engine. An additional benefit of smaller internal combustion engines is that the weight of the engine is reduced, thereby achieving improved performance, i.e. acceleration, while achieving greater fuel economy. Contemporary internal combustion engine design has witnessed the trend of operating engines at a higher temperature to improve their fuel efficiency and incorporating multiple valves per cylinder into the engine design to improve the intake of combustion air and the discharge of the products of combustion. Additionally, the trend toward reducing the weight of engines has seen the use of engine components, for example engine blocks and cylinder heads, having thinner castings to reduce unnecessary weight. The trend toward lighter weight castings is particularly evident in the design and manufacture of cylinder and becomes especially critical in cylinder heads designed for engines having more than two valves per cylinder, for example, in cylinder heads with two intake and two exhaust valves per cylinder.
Cylinder blocks and cylinder heads for internal combustion engines are now widely manufactured using a casting process in which a sand mold is used to define passages and other openings in a hot metal (e.g. cast iron) casting. A known problem associated with using sand molds for casting such components is that the mold may be damaged prior to or during the casting process, or may otherwise contain imperfections which replicate themselves in the cast parts. For example, it is common to manufacture a cylinder head using a sand casting process and, if the mold has defects in the areas defining the water passages in the cylinder head, the water passages will contain defects. Such defects may take a form of restrictions within one or more of the water passages which restrict the flow of water and, as a result, cause localized heating within the cylinder head during operation of the engine. It is necessary to incorporate multiple water cooling passages or cavities within a cylinder head designed for operation at high engine temperatures to remove the heat byproduct of combustion which, if allowed to remain within the cylinder head, would cause unacceptable thermal expansion and possible premature failure of the cylinder head or other engine components, for example intake or exhaust valves. More particularly, cylinder heads utilizing two or more intake and exhaust valves per cylinder are manufactured with multiple water passages in the vicinity of each valve to insure that the cylinder head in the vicinity of each of the valves does not distort or buckle from excessive heat. Consequently, the water passages' ability to remove heat from the area of the cylinder head surrounding each valve becomes critical to the reliable operation and longevity of the engine.
Various known methods and apparatus have been used in the past to test the water passages in a cylinder head for blockages. For example, U.S. Pat. No. 3,360,984 discloses a mechanism for testing engine parts such as cylinder heads and the like by the use of a pressurized fluid. In particular, the disclosed apparatus includes a mechanism for supporting the cylinder head or other component under test and for selectively sealing ports on the cylinder head to permit the cylinder head or other component to be pressure tested using a pressurized fluid introduced into the interior cavity of the component undergoing test. While the mechanism disclosed in the '984 patent permits selective sealing of apertures in a component undergoing test to provide for flexibility of testing a variety of components having different orifice configurations, it nevertheless still requires the use of a pressurized fluid source.
U.S. Pat. No. 3,608,369 discloses an engine head test stand to permit applying water under pressure to an engine cylinder head while sealing openings in the engine head to determine the presence of leaks.
U.S. Pat. No. 3,973,429 discloses a test apparatus for engine heads consisting of a means for supplying fluid from a pressurized source into various cavities in a cylinder head and means for selectively sealing various of the ports of the cylinder head to permit fluid under pressure to be forced into selected passages within the cylinder head to test for leakage. The apparatus permits pressure hoses to be connected to selected ports and the sealing of other ports so that passages within the cylinder head can be selectively tested. Cracks are detected in the head by listening for the escape of air and/or observing the escape of water pressurized within the cylinder head by an air supply.
U.S. Pat. No. 4,860,575 discloses an apparatus for testing the heads of an internal combustion engine for fluid tightness by sealing internal cavities in the head under test from the atmosphere and then applying air pressure to the cavities. While the engine head is under pressure, a soapy solution is applied to the head so that leaks of air from within the internal cavities can be detected by visual observation.
U.S. Pat. No. 5,095,738 discloses an internal combustion engine head leak tester which includes a cover for positioning on an engine head to cover coolant passage ports and means for clamping the head cover onto the head to seal the passages. The invention disclosed in the patent provides means for quickly clamping a head cover onto the head for covering coolant passages ports of the head and means for applying fluid under pressure to the coolant passages within the head.
U.S. Pat. No. 3,874,225 discloses an apparatus for pressure testing injector sleeves of diesel engine heads comprising a means for providing a seal to isolate a portion of a cavity of the cylinder head in which the injector sleeve is contained and means for introducing compressed air into the interior of the sleeve. A pressure gauge on the tester detects any leakage past the injector sleeve after a valve is closed to seal the injector sleeve from the compressed air supply. The foregoing prior art can broadly be classified as disclosing either apparatus for facilitating the testing of cylinder heads for leaks by introducing a liquid or gas into the cylinder head after selected ports within the cylinder head have been closed off and observing leakage of the fluid from the cylinder head, or as disclosing apparatus for the selective sealing of cavities within the cylinder head and the introduction of a gas under pressure into the sealed-off cavity for observing the pressure of the gas to detect fluctuations caused by leakage of the gas from the cylinder head. However, each of the disclosed apparatus is deficient in that they require substantial manual intervention in the testing process, and do not disclose a means for efficiently and automatically collecting information on the test process and comparing the cylinder head under test to a cylinder head having known, acceptable characteristics. Consequently, there is a need for an apparatus and a method for testing engine components in general, and cylinder heads in particular for leakage in the water passages or other fluid-carrying passages which will permit the rapid, automatic testing of the component undergoing testing and which will permit the efficient, automatic collection of data for use in automated assembly line operations.
The known prior art is also deficient in that it does not disclose a mechanism which will permit quantitative information concerning restrictions, if any, in water cooling passages of a cylinder head to be gathered, and to compare such information to the physical characteristics of equivalent water passages in a cylinder head known to have no defects in its fluid-carrying passages. Thus, the desirable traits of a water cavity flow test apparatus and method would include the ability of the apparatus to automatically test the cylinder head or other engine component undergoing test by selectively sealing off fluid-carrying passages in the component undergoing test to pinpoint the location of defects within the component, and the automatic collection of data relating to the ability of the passages within the component undergoing test to conduct fluids such as cooling water. A further desirable attribute of such an apparatus would be the ability to compare the data gathered from the object undergoing test to data collected from a known equivalent object having acceptable fluid-carrying passages and to be able to accept or reject the object under test on the basis of a comparison of the data collected for the object undergoing test to data previously collected for a sample of the object known to be defect-free.